Control of elevator hoist and door motors



Feb. 18, 1969 H. A. STAINKEN 3,428,878-

CONTROL OF ELEVATOR HOIST AND DOOR MOTORS Filed May 4, 1964 Sheet of 4 GF 28 3 L.

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Filed May 4, 1964 IOl Sheet ,2 01'4 FIG. 30

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HENRY AUGUST STAINKEN INVENTOR BY MZW ATTORNEY United States Patent Oflice 3,428,878 Patented Feb. 18, 1969 12 Claims ABSTRACT OF THE DISCLOSURE An elevator system including an elevator car, a hoist motor for raising and lowering said car, said hoist motor having an armature and a field winding, 2. supply of substantially constant unidirectional voltage to which said hoist motor field winding is connected, a continuously rotating generator having an armature and a principal field winding and a levelling field winding, means interconnecting said armatures of said hoist motor and said generator, a door on said car, a door motor for opening and closing said door, said door motor having an armature and a field winding, said door motor field winding being connected to said supply, a unidirectional voltage source of variable magnitude, a plurality of control circuits selectively connectable to said source for varying the output voltage thereof as a different predetermined function of time, and switch means for selectively connecting either said door motor armature and one of said control circuits to said source or said principal field winding and another of said control circuits to said source and for connecting said levelling field winding to said supply.

This invention relates generally to elevator systems and particularly to systems for controlling the operation of both the hoist motor and the car door motor.

Elevator systems require a hoist motor which must be controlled to provide smooth acceleration and decleration of the car. Such control is usually obtained by varying the voltage applied either directly to the motor or, more commonly, to the field winding of a generator which, in turn, supplies power to the hoist motor. Various systems for obtaining variable voltage have been proposed such as systems using a series resistor which is inserted or removed from the circuit in steps, system using saturable reactors, and systems using controlled rectifiers such as thyratrons or silicon controlled rectifiers. In any case, the system supplies a voltage which varies as a function of time, increasing during acceleration and decreasing during deceleration.

It is common practice to provide an electric motor for opening and closing the car and hoistway doors and this motor must also be supplied with a varying voltage at the proper time in order to open and close the doors smoothly. Various arrangements of step controlled series resistors, saturable reactors, and controlled rectifiers have also been proposed for controlling the door motor.

The usual elevator system includes a source of variable voltage for controlling the hoist motor and an additional source of variable voltage for controlling the door motor. Variable voltage sources whether comprising resistors and relays, saturable reactors, controlled rectifiers or combinations thereof are expensive and a significant reduction in cost could be achieved if it were possible to use the same source for controlling both the hoist motor and the door motor. At first glance it would appear to be a simple matter to switch a single source from one motor to another as required. However, certain difiiculties arise. For example, it must be realized that a voltage variation suitable for accelerating the hoisting motor may be quite different from a voltage variation suitable for accelerating the door motor. As another example, it is the usual practice to start the door opening operation as the car approaches the landing before the hoisting motor has been completely deenergized thereby requiring that both motors be controlled simultaneously.

It is a general object of the present invention to reduce the cost of an elevator installation without degrading the performance in any way.

A more specific object of the invention is to utilize the same variable voltage source for controlling both the hoist motor and the door motor.

Another object is to utilize the same source for both the hoist and door motors yet provide each with a voltage variation suitable for its own requirements.

Another object is to utilize the same variable voltage source for both motors yet allow the doors to commence opening in advance of the stopping of the car.

Briefly stated, a preferred embodiment of the invention comprises a source of electric energy of controllable magnitude, such as a pair of thyratrons connected as a full wave rectifier. Several control circuits are provided, each of which, when connected to the source, causes the output voltage to vary as a predetermined function of time. For example, the output voltage may be caused to increase at a predetermined rate from zero to a predetermined maximum or may be caused to decrease from a maximum to zero. A switching system is provided which selectively connects the output of the source to control either the hoisting motor or the door motor and at the same time connects the appropriate control circuit. The invention has particular application to an elevator system in which the hoisting motor is controlled principally by a first generator field winding during acceleration, running and deceleration, and solely by a second generator field winding during fine levelling. The first field winding and the door motor are energized by the variable source while the second winding is energized by a separate source. When the car is to be stopped, the proper control circuit is connected to decrease the energization of the first winding. Just before the car reaches the landing, the first winding is disconnected from the variable source, allowing the second winding to complete the levelling operation. This permits the variable source to be connected to start opening the door before the car has completely stopped.

For a clearer understanding of the invention reference may be made to the following detailed description and the accompanying drawing, in which:

FIGURE 1 is a schematic diagram of an elevator system;

FIGURE 2 is a schematic diagram showing the function of the levelling switches;

FIGURES 3a and 3b taken together are a schematic wiring diagram of a simplified elevator system incorporating the invention;

FIGURES 4, 5, 6 and 7 are graphs useful in explaining the invention;

FIGURE 8 is a key diagram showing in spindle form the relationship of the coils and contacts shown in FIG- URES 3a and 3b; and

FIGURE 9 is a block diagram, which schematically illustrates the simplified elevator system incorporating the invention.

Referring first to FIGURE 1 there is shown an elevator car 21 with a door 22 slidably horizontally to either an open or a closed position. The door 22 is opened and closed by a reversible motor DM mounted on the car frame and mechanically connected to the door by a suitable mechanism. This mechanism is illustrated schematically as comprising a rack 23 mounted on the door and a pinion 24 mounted on the car frame engaging the rack and driven by the motor DM. It is to be understood that FIGURE 1 is schematic only and that any of various known door operating mechanisms can be used instead of the rack and pinion shown.

The door 22 is illustrated in partly opened position. When it is substantially fully opened the door 22 engages a door open limit switch DOL mounted on the car frame and when substantially fully closed it engages a door close limit switch DCL also mounted on the frame. The door 22 is preferably provided with the usual hydraulic cushioning devices (not shown) which operate at each limit of travel to prevent jarring and provide gentle stops as the door is opened and closed.

The car 21 is raised and lowered by one or more ropes 25 which pass over a traction sheave 26 and which are fastened at one end to the car 21 and at the other end to a suitable counterweight 27. A mechanical brake 28 is applied by a spring (not shown) and released by the energization of a brake coil BR. The sheave 26 is driven by a direct current hoisting motor 31 mechanically connected thereto. The field winding MP is connected to a source of direct current while the armature is connected to the armature of a direct current generator 32 which is driven continuously by a suitable prime mover (not shown). The generator 32 is provided with a principal field winding GF and a levelling field winding GLF, the connections to which will be described subsequently. It will be understood that the motor 31 and the generator 32 may each be provided with additional field windings such as compensating windings, interpole windings, etc., as is common practice in the art.

The position of the car 21 is reproduced to a reduced scale by a selector 34 located in the machine room. A perforated steel tape 35 passes over sprockets 36 and 37 located in the machine room and the pit, respectively, and has its opposite ends connected to the car 21. The sprocket 36 is operatively connected to and drives the selector 34. The selector 34 may be any of several well known varieties most of the details of which are not pertinent to the present invention. However, the selector 34 includes a levelling assembly 38 indicated by the dotted outline within the selector 34, the function of which is shown schematically in FIGURE 2.

Referring now to FIGURE 2 there are shown cams 41 and 42 the angular position of which represents the position of the car 21 with respect to a landing. These cams are shown in the position they occupy when the car is at a landing. The frame 43 carries two switches LV1 and LV2 which are open, as shown, when the car is at the landing but one or the other of which is closed by the cam 41 when the car departs by a slight amount from the level position. The frame 44 carries two switches LV3 and LV4 one or the other of which is opened by the cam 42 when the car approaches the levelling zone and both of which are opened when the car is within a short predetermined distance from the landing. The switches LV1 and LV2 respond to less movement of the car than the switches LV3 and LV4, that is, as the car departs from the landing one of the switches LV1 or LV2 closes before either of the switches LV3 or LV4 is opened. The frames 43 and 44 are mechanically connected together and are biased by a spring (not shown) or gravity to the position shown but may be withdrawn by the energization of a coil LV so that the switches cannot be engaged by the cams regardless of the orientation of the cams. When so withdrawn, the switches LV1 and LV2 are open while the switches LV3 and LV4 are closed. When the coil LV is deenergized, the condition of the switches is determined by the position of the cams.

It is to be understood that the showing of FIGURE 2 is schematic only and that any physical construction may be used which will cause the switches to be operated as explained.

Referring now to FIGURE 3b, there are shown a pair of thyratron tubes 51 and 52 which, with their associated circuits, comprise a source of unidirectional voltage of variable magnitude. The anodes 53 and 54 are connected to opposite ends of the secondary winding of a transformer 55 the primary winding of which is connected to a source of alternating voltage. The center tap of the secondary winding is connected to a conductor 56 which comprises one output conductor of the variable magnitude source. The cathodes 57 and 58 are connected together and to a conductor 59 which comprises the other output conductor of the variable magnitude source. This source is used to supply energy to the principal generator field windng GF and to the armature DMA of the door motor through circuits to be described subsequently. The magnitude of the voltage, and consequently the current supplied to the load circuit, is controlled by varying the phase of an alternating voltage applied to the grids 61 and 62, as will be more fully explained.

FIGURE 4 illustrates how the current through the principal generator field winding GF is varied. When the car is at rest the current is zero. When the car is to be accelerated the current through the winding GF increases gradually as shown by the left-hand portion of the curve 65 until a maximum is reached. This maximum current remains substantially constant while the elevator is running between floors as shown by the dotted portion of the curve 65. When the elevator is to be stopped the current decreases smoothly to zero.

FIGURE 5 depicts the current flowing through the armature of the door motor as the door is opened. As shown by the curve 66, the current rises rapidly to a maximum so that the door accelerates quickly to its maximum speed. This maximum current will, in general, be different from the maximum current required for energization of the main generator field winding. The maximum is constant during the door opening operation as shown by the dotted portion of the curve 66 and as the door approaches the fully opened position, the hydraulic cushioning mechanism (not shown) slows down the door providing a smooth stop and when the door is substantially fully opened, a circuit is opened whereupon the current decreases rapidly to zero.

The current required for the door closing operation is similar, as shown in FIG. 6. However, the door closes more slowly than it opens and, accordingly, as shown by the curve 67, the maximum current is not as large as during door opening. When the door approaihes the fully closed position, the cushioning mechanism retards the door smoothly and when substantially fully closed, a circuit opens whereupon the current falls rapidly to zero.

Referring again to FIGURE 3b there is shown a saturable reactor 71 indicated generally by the dotted outline. The reactor includes two alternating current windings 72 and 73 the inductance of which are to be controlled, and three control windings 74, 75 and 76 through which direct current is passed to vary the reluctance of the magnetic circuit and the inductance of the alternating current windings 72 and 73. The latter windings are connected in parallel and the combination is connected in series with a variable resistor 77 and this series combination is connected to the extremities of the secondary winding of a transformer 78 the primary winding of which is connected to the same source of alternating current to which the primary winding of the transformer 55 is connected. The junction of the resistor 77 with the windings 72 and 73 is connected to one terminal of the primary winding of a peaking transformer 79 the other extremity of which is connected to the center tap of the secondary winding of the transformer 78. The extremities of the secondary winding of the peaking transformer 79 are connected through current limiting resistors 81 and 82 to the grids 61 and 62 of the thyratron tubes 51 and 52. The center tap of the secondary winding of the transformer 79 is connected to the adjustable tap of a resistor 83. A substantially constant unidirectional voltage is connected across the resistor 83. The positive terminal of this source is connected to the cathodes 57 and 58. The circuit including the windings 72 and 73, the transformer 78 and the resistor 77 comprise a circuit for varying the phase of the voltage applied to the primary winding of the transformer 79 as the inductance of the windings 72 and 73 is varied. The transformer 79 converts the substantially sine wave input to a peaked waveform which is applied to the grids 61 and 62. The D.C. bias provided through the resistor 83 serves to adjust the peak potential of the grid voltage with respect to the potential of the cathodes 57 and 58.

FIGURE 7 shows the familiar representation of one half-cycle of the voltage applied to the anode of one of the thyratrons 51 or 52. The curve 85 represents the anode voltage, the axis 86 represents the cathode potential, and the dotted curve 87 represents the critical grid voltage. The parameters of the previously described phase shifting circuit are selected so that with no current flowing in any of the DC. control windings 74, 75 and 76, the peak voltage applied to the grid occurs at the end, or just beyond the end, of the positive half-cycle of the anode voltage as shown by the waveform '88. As the current is increased in one of the control windings 74, 75 or '76, the inductance of the windings 72 and 73 decreases, the phase shift decreases, and the waveform moves to the left, as viewed in FIGURE 7, causing the thyratron to conduct for a portion of each half-cycle. As shown in FIGURE 3b the thyratrons 51 and 52 are connected in a full wave rectifying circuit and each tube operates similarly but on oppposite half-cycles.

It is apparent from the above that the thyratrons 51 and 52 and their associated circuits comprise a variable voltage source, the magnitude of which depends upon the electrical magnitude of a circuit element, namely, upon the inductance of the windings 72 and 73. As will be more fully explained the inductance of windings 72 and 73 is varied by operatively connecting one of a plurality of control circuits which varies the current through one of the DC. windings 74, 75 or 76.

The remainder of the apparatus can best be understood by considering the operation of the circuit of FIGURES 3a and 3b. The following is a list of electromagnetic switches and relays which are used in this circuit:

XU-Up Direction Relay XDDown Direction Relay DODoor Open Relay DC-Door Close Relay UXUp Operation Relay DX-Down Operation Relay SStart Relay UUp Levelling Relay D-Down Levelling Relay LV-Cam Levelling Assembly In addition to the above relays the apparatus includes the previously mentioned door open limit switch DOL and the door closed limit switch DCL; a car door switch CDS and a hoistway door switch HDS which switches are closed only when the respective doors are fully closed; a manually operated door opening button switch DOB; a manually operated door closing button switch DCB; and manually operated switches 91, 92 and FIGURES 3a and 3-b show the relays in their deenergized condition and show the various switches in the positions which they occupy when the car is at rest at a landing with the doors open. As shown, the field winding DMF of the door motor is permanently connected to direct current supply conductors 101 and 102. The switch 91 selects the direction of travel of the elevator and is shown selecting the up direction in which the relay winding XU is energized. Energization of the winding XU closes the normally open contacts XU1. To start the operation the door closing switch DCB is operated; a circuit is completed from the conductor 101 through the switch DCB, the normally closed contacts D04, the switch DCL, the door closing relay DC, and normally closed contacts UXl and DX1 to the conductor 102. The winding DC is energized thereby closing contacts DCl, DC2 and DC3 and opening contacts DC4. Contacts D01 and DC2 connect the door motor armature DMA to the conductors 56 and 59 through the normally closed contacts UX3 and DX3. Closure of contacts DC3 connects a first control circuit to the conductors 101 and 102 as will be explained below. The opening of contacts DC4 disables the door opening circuit.

As shown in the upper portion of FIGURE 3b, the first control circuit may be traced through the contacts DC3, a tapped resistor 103, a variable resistor 104, and the DC. control winding 75 to the conductor 102. A capacitor has one plate connected to the junction of the winding 75 with the conductor 102 and the other plate connected to the adjustable tap of the resistor 103. The capacitor 105 is initially discharged and when the first control circuit is completed by closure of contacts DC3, the capacitor constitutes a low impedance path shunting the winding 75 so that the winding 75 draws very little current. As the capacitor 105 charges through the resistor 103, the current through the winding 75 gradually increases, reaching a maximum steady state value when the capacitor is fully charged. During this time the magnetic field intensity in the core of the saturable reactor 71 increases, decreasing the inductance of windings 72 and 73, decreasing the phase shift, and causing the peaked voltage applied to the grids 61 and 62 to shift to the left, as viewed in FIGURE 7, from the position of the waveform 88 towards the position of the waveform 89. The current through the armature DMA of the door motor increases as shown in FIGURE 6 reaching its maximum as the capacitor 105 becomes fully charged. The resistor 104 may be varied to adjust the maximum current and the tap on resistor 103 may be varied to adjust the time constant of the charging circuit of the capacitor 105.

When the door approaches its fully closed position the hydraulic cushioning mechanism retards the door providing a smooth stop. When the door is substantially fully closed the door closed limit switch DCL is opened thereby deenergizing the winding DC, opening the contacts DCI, DC2 and DC3 and closing the contacts DC4. The opening of contacts DCl and DC2 disconnects the motor armature DMA from the conductors 56 and 59 causing the current to fall rapidly to zero; the opening of contacts DC3 disconnects control winding 75 and its associated circuit allowing the capacitor 105 to discharge through the winding 75 but this has no elfect at this time because the armature DMA has been disconnected. Closure of the contacts DC4 reenables the door opening circuit to be ready for the next door opening operation. Closure of the door also closes the car door switch CD8 and the hoistway door switch HDS.

To start the elevator, the switch 93 is closed momentarily. The start relay S is energized closing its contacts S1, S2, S3 and S5 and opening its contacts S4. The closure of S1 energizes the levelling coil LV, retracting the switches LV1, LV2, LV3 and LV4 from the cams. Cams similar to the cams 41 and 42 are provided for each floor and the retraction of the switches prevents their actuation except at a floor at which it is desired to stop the elevator. Closure of S2 shunts the switches LV3 and LV4 establishing a circuit through the contacts XU1 to the relay coil UX. Closure of contacts S3 partially completes a second control circuit which includes the winding 74. Contacts S4 open for a purpose to be described subsequently. Closing of contacts S5 completes a seal in circuit around the manual switch 93 so that the relay winding S remains energized even though the switch 93 be released.

As mentioned above, the relay 'UX is energized through the contacts S2. Contacts UX1 open disabling the door opening and door closing relays. Contacts UX2 close completing the circuit to the winding 74. This second control circuit may be traced from the conductor 101 through the contacts UX2 and S3, a tapped resistor 107', a variable resistor 108 and the winding 74 to the conductor 102. One plate of a capacitor 109 is connected to the junction of the winding 74 with the conductor 102 while the other plate is connected to the tap of the resistor 107. This control circuit operates in much the same way as does the previously described circuit. Since the contacts S4 are open, the circuit is identical except for the sizes of the parameters. These are chosen and adjusted to make the current through the winding 74 rise at the proper rate and reach the proper maximum value so that the current through the field winding GF causes the hoist motor 31 to accelerate at the desired rate and reach the desired maximum speed.

At the same time, the contacts UX4 and UXS close thereby connecting the principal generator field winding GP to the conductors 56 and 59. Also the contacts UX6 close shunting the switch LV1 and completing a circuit from the conductor 101 through the contacts DX7 to the relay winding U. Contacts U1 and U2 close energizing the levelling field winding GLF and the brake Winding BR allowing the elevator car to start. Contacts UX7 open thereby disabling the down levelling relay D. Contacts UXS close shunting the contacts XU1 so that the coil UX may remain energized even if the direction switch 91 should be operated while the elevator car is in motion.

Summarizing the principal effects of operating the switch 93, a gradually increasing voltage is applied to the generator field winding GF and at the same time the levelling field winding GLF is connected to the conductors 101 and 102 so that the elevator is accelerated to full running speed.

To stop the elevator the switch 92 is depressed momentarily. This deenergizes the relay S opening the switches S1, S2, S3 and S5 and closing the switch S4. Opening of contacts S1 deenergizes the levelling relay coil LV allowing the switches LV1, LV2, LV3 and LV4 to be controlled by the cams 41 and 42. The opening of contacts 52 partially opens the circuit to the up operation relay UX but the circuit is maintained through the switches LV3 and LV4. Opening of the contacts S3 opens the circuit between the conductor 101 and the resistor 107. Closure of the contacts S4 connects a resistor 111 across the plates of the capacitor 109. This circuit together with the resistors 107, 108 and the winding 74 can be thought of as a third control circuit. When this circuit is first established capacitor 109 is fully charged but immediately starts to discharge through the resistor 111. As the discharge proceeds the current through the winding 74 decreases thereby increasing the inductance of the winding 72 and 73, increasing thephase shift, and causing the current through the main generator field winding GP to decrease as shown by the right-hand side of the curve 65 of FIGURE 4. Opening of contacts S5 breaks the seal in circuit around the start switch 93.

The elevator is now decelerating. The main generator winding GF is still in the circuit because the relay UX is still energized. When the car reaches the levelling zone the switches LV3 and LV4 open deenergizing the relay UX. Closure of contacts UX1 partially reestablishes the circuit to the door open relay DO. Opening of contacts UX2 further opens the energizing circuit of the winding 74. Closure of contacts UX3 partially establishes a circuit to the door motor armature DMA. Contacts UX4 and UXS open thereby disconnecting the field winding GF from the conductors 56 and 59. The opening of contacts UX6 would deenergize the up levelling relay U except that the switch LV1 is still closed provided that the car is not yet completely level with the landing. Closing of UX7 partially completes a circuit to the down levelling relay D. Opening of contacts UXS further disables the circuits of the relay coil UX.

At this time the generator levelling field winding GLF is still energized and the car is brought slowly to the landing at which time the switch LV1 opens. This deenergizes the up levelling relay U which, through opening of its contacts U1 and U2, disconnects the field winding GLF and deenergizes the brake winding BR thereby stopping the car and holding it stationary.

The above operation has been described in connection with up operation of the elevator. It is obvious that a similar sequence of events would occur during down operation except that the relays XD, DX and D would be energized instead of the relays XU, UX and U.

The car having been brought to a stop at the landing the door may 'be opened. The door opening button switch DOB is closed completing a circuit through the contacts DC4, the switch DOL and the contacts UX1 and DXl thereby energizing the relay DO. It is to be noted that this circuit can be completed before the car stops provided that it is in the levelling zone so that principal field winding GF is deenergized by the deenergization of the relay UX. At this time, the car is very near to the landing and is moving very slowly since only the levelling field winding GLF is operative. Energization of relay D0 closes contacts D01 and D02 connecting the armature DMA to the conductors 56 and 59. Closure of contacts D03 completes a fourth control circuit from the conductor 101 through the contacts D03, a tapped resistor 115, a variable resistor 116 and the coil 76 to the conductor 102. A capacitor 117 is connected between the tap on resistor and the junction of the Winding 76 with the conductor 102. This circuit operates in the same way as previously explained in connection with the winding 75 to cause the current through the door motor armature DMA to rise as shown by the curve 66 of FIGURE 5. It is to be noted that the current applied during the door opening operation is greater than during door closing because there is no danger of striking passengers at this time. The door accelerates rapidly to its full speed and opens quickly. When the door is substantially fully opened the door opening limit switch DOL opens, thereby deenergizing the relay D0. At substantially the same time the hydraulic cushioning mechanism retards the door bringing it smoothly to a stop. Contacts D01 and D02 open, disconnecting the armature DMA, causing the current to fall rapidly to zero. Contacts D03 disconnect the conductor 101 from the control circuit to the winding 76. The capacitor 117 discharges through the winding 76 but has no efiect on the door since the armature DMA has been disconnected. The contact D04 closes partially completing a circuit to the door closing relay DC.

Opening of the car and hoistway doors opens the switches CD8 and HDS thereby preventing energization of the relays UX or DX so that the main generator field winding cannot *be energized. However, it is to be noted that, provided relays UX and DX are deenergized so that contacts UX7 and DX7 are closed, either relay U or D can be energized by closure of the switches LV1 or LV2 even though the doors are open. If the load on the car changes greatly due to passengers entering or leaving, it

is possible for the hoisting ropes to stretch or contract or to slip slightly causing the car to move slightly away from the landing. In such a case one of the switches LV1 or LV2 will close thereby energizing the appropriate relay U or D to connect the generator levelling field winding GLF with the proper polarity to return the car slowly to the landing.

It is apparent from the foregoing description that the present invention provides a system for selectively energizing either of two load devices, namely the door motor armature DMA or the principal generator field winding 'GF, from the same variable voltage source. With either load connected to the output, the source can be controlled to provide an output voltage which varies as any one of a plurality of functions of time. Selection of the desired function is achieved by the provision of a plurality of control circuits and by connecting the desired control circuit simultaneously with the connection of the desired load. Although it is preferred at present to use separate control windings, capacitors, resistors, etc., it is obvious that the separate circuits could be established by a switching system which rearranges fewer components.

It must be remembered that a modern elevator installation is an extremely complicated system. In the present application there are shown only those elements which are necessary for a complete understanding of the instant invention. It is obvious that the circuits established by the manually operated switches DOB, DOB, 91, 92 and 93 could, and normally would, be established automatically in response to various signals such as those from car buttons, hall buttons and elevator programming devices. Likewise it is obvious that more sophisticated door opening and closing arrangements could be provided such as arrangements using decreasing energization as similar to that shown for the generator field winding, spring assisted door closing, and/or low level energization of the door motor when stalled with the doors fully opened or closed to bias the doors in the desired direction. These are but a few of the many refinements which might be made in a commercial installation. Variations include other kinds of sources of controllable magnitude .such as saturable reactors carrying the load current or silicon controlled rectifiers. However, thyratrons are preferred at present because they are rugged and easily controlled. Many other modifications within the spirit of the invention will occur to those skilled in the art. It is therefore desired that the protection afforded by Letters Patent be limited only by the true scope of the appended claims.

What is claimed is:

1. An elevator system, comprising:

an elevator car,

a hoist motor and generator, including a generator principal field winding and a generator levelling field winding, for raising and lowering said car,

a door on said car,

a door motor for opening and closing said door,

a main source of voltage of controllable magnitude,

control means for controlling said main source, when connected thereto, to provide selected ones of a plurality of voltage variations with respect to time to said door motor and said hoist motor,

a secondary source of voltage of substantially constant magnitude, and

means for selectively connecting either said door motor and said control means to said main source or said principal field winding and said control means to said main source and for connecting said levelling field winding to said secondary source while either said door motor or said principal field winding is connected to said main source.

2. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature, for raising and lowering said car,

a continuously rotating generator including an armature, a principal field winding and a levelling field Winding,

means interconnecting said armatures of said vhoist motor and said generator,

a door on said car,

a door motor, including an armature, for opening and closing said door,

a main source of voltage including a circuit element the electrical magnitude of which determines the output voltage,

a plurality of control circuit means each, when operatively connected to said main source, for varying the electrical magnitude of said element as a different predetermined function of time,

a secondary source of voltage of substantially constant magnitude, and

switch means for selectively connecting either said door motor armature and one of said control circuit means to said main source or said principal field winding and another of said control circuit means to said main source and for connecting said levelling field winding to said secondary source while either said door motor armature or said principal field winding is connected to said main source.

3. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature and a field winding, for raising and lowering said car,

a supply of substantially constant unidirectional voltage, said field winding being connected to said pp y,

a continuously rotating generator including an armature, a principal field winding and a levelling field Winding,

means interconnecting said armatures of said hoist motor and said generator,

a door on said car,

a door motor, including an armature and a field winding, for opening and closing said door,

said door motor field winding being connected to said pp y.

a saturable reactor including an alternating current winding and direct current control windings,

a source of voltage including said alternating current winding the inductance of which determines the output voltage,

a plurality of circuit means each including one of said control windings and each, when operatively connected, for varying the current through its control winding as a different predetermined function of time, and

means for selectively connecting either said door motor armature to said source and one of said circuit means to said reactor or said principal field winding to said source and another of said circuit means to said reactor and for connecting said levelling field winding to said supply while either said door motor armature or said principal field winding is connected to said source.

4. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature and a field winding, for raising and lowering said car,

a supply of substantially constant unidirectional volttage,

said field winding being connected to said supply,

a continuously rotating generator including an armature and a field winding,

means interconnecting said armatures of said hoist motor and said generator,

a levelling device acting independently of said generator field winding to bring said car level with a floor,

a door on said car,

a door motor, including an armature and a field winding, for opening and closing said door,

said door motor field winding being connected to said pp y,

a source of electrical energy of controllable output voltage,

a plurality of circuit means each, when operatively connected, for controlling the output voltage of said source,

one of said circuit means providing an output voltage which increases from zero to a first predetermined magnitude,

another of said circuit means providing an output voltage which increases from zero to a second predetermined magnitude, and

means selectively connecting either said door motor armature and said one of said circuit means to said source or said generator field winding and the other of said circuit means to said source and for connecting said levelling device to said supply while either said door motor armature or said generator field winding is connected to said source.

5. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature and a field winding, for raising or lowering said car,

a supply of substantially constant unidirectional voltage, said field winding being connected to said supply,

a continuously rotating generator including an armature, a principal field winding and a levelling field winding,

means interconnecting said armatures of said hoist motor and said generator,

a door on said car,

a door motor, including an armature and a field winding, for opening and closing said door,

said door motor field winding being connected to said pp y,

a source of voltage of controllable magnitude,

first, second, third and fourth circuit means each for controlling the output voltage of said source in accordance with a different predetermined function of time,

said first circuit means providing an output voltage suitable for controlling said hoist motor in acceleration,

said second circuit means providing an output voltage suitable for controlling said hoist motor in deceleration,

said third circuit means providing an output voltage suitable for controlling said door motor to open said door,

said fourth circuit means providing an output voltage suitable for controlling said door motor to close said door, and

means selectively connecting either said door motor armature and said circuit means to said source or said principal field winding and said circuit means to said source and for connecting said levelling fluid winding to said supply while either said door motor armature or said principal field winding is connected to said source and for disconnecting said levelling field winding from said supply While said door motor armature is connected to said source.

6. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature and a field winding, for raising and lowering said car,

a supply of substantially constant unidirectional voltage, said field winding being connected to said supply,

a continuously rotating generator including an armature, a principal field winding and a levelling field winding,

means interconnecting said armatures of said hoist motor and said generator,

a door on said car,

a door motor, including an armature and a field winding, for opening and closing said door,

said door motor field winding being connected to said voltage supply,

a main alternating current source,

a supply of alternating current,

control circuit means connected to said alternating current supply,

a controllable rectifier connected to said main source for providing a unidirectional voltage output of variable magnitude,

said rectifier including control element means when connected to said control circuit means, for varying the output voltage in accordance with the phase of said control circuit means with respect to said main source,

said control circuit means including a plurality of control circuits each for varying the phase of said control circuit means as a different predetermined function of time, and

switching means for connecting either said door motor armature and said control circuit means to said rectifier or said principal field winding and said control circuit means to said rectifier and for connecting said levelling field winding to said voltage supply while either said door motor armature or said principal field winding is connected to said rectifier and for disconnecting said levelling field winding from said voltage supply while said door motor armature is connected to said rectifier.

7. Apparatus according to claim 6 in which said controllable rectifier comprises a pair of thyratron tubes and in which said control element means comprises control electrodes in said thyratron tubes.

8. Apparatus according to claim 7 in which said control circuit means includes a phase shifting circuit wherein the phase is varied by varying the inductance of an alternating current winding of a saturable reactor and in which each of said control circuits includes a direct current winding of said saturable reactor.

9. An elevator system, comprising:

an elevator car,

a hoist motor, including an armature and a field winding, for raising and lowering said car,

a supply of substantially constant unidirectional voltage,

said field winding being connected to said supply,

a continuously rotating generator including an armature, a principal field winding and a levelling field Winding,

means interconnecting said armatures of said hoist motor and said generator,

a door on said car,

a door motor, including an armature and a field winding, for opening and closing said door,

said door motor field winding being connected to said a unidirectional voltage source of variable magnitude,

a plurality of control circuits selectively connectable to said source for varying the output voltage thereof as a different predetermined function of time, and

switch means for selectively connecting either said door motor armature and one of said control circuits to said source or said principal field winding and another of said control circuits to said source and said levelling field winding to said supply.

10. Apparatus according to claim 9 in which said switch means includes means for connecting either one of two of said control circuits and said door armature with either polarity to said source for opening said door quickly or closing said door slowly.

11. Apparatus according to claim 9 in which said switch means includes means for connecting said principal field winding and said levelling field winding to said source and said supply respectively with either polarity to raise or lower said car.

13 14 12. Apparatus according to claim 11 in which said 2,931,462 5/ 1960 Heart 187-29 switch means includes means for connecting either one of 3,174,086 3/1965 Gorjanc 318-103 two of said control circuits to said source for controlling said hoist motor in acceleration or deceleration. ORIS L. RADER, Primary Examiner.

References Cited 5 T. E. LYNCH, Assistant Examiner.

UNITED STATES PATENTS 1,778,465 10/ 1930 Ozanne. 2,643,741 6/ 1953 Esselman 187-29 3 18-1 5 8; 18729 2,867,292 1/ 1959 Bruns 187-29 10 U.S. C1. X.R. 

